Effects of age and gender on CNS serotonergic responsivity in normal adults.

The effects of age and gender on central nervous system (CNS) serotonergic responsivity were assessed with a neuroendocrine challenge test in 30 normal adults. Subjects greater than or equal to 30 years of age, compared with younger subjects, exhibited decreased prolactin secretion in response to a 60-mg oral dose of dl-fenfluramine hydrochloride, an indirect serotonin agonist. Furthermore, women had greater prolactin responses than men. As prolactin secretory capacity appears to be stable through midlife, the age-associated decrease in fenfluramine-induced prolactin release suggests a decline in CNS serotonergic responsivity. In contrast, the finding of greater prolactin release in women than in men probably reflects the effects of nonserotonergic modulatory influences at the level of the lactotroph. Age and gender effects must be considered in studies of the CNS serotonergic system.